Various techniques are known from the state of the art for making bores, counter-sinking or saw cuts with a predetermined spatial orientation and depth. One known technique is the marking of the work piece with a point or line, whereby the point can be the middle point of a bore and the line can be the course of a saw cut.
In order to be able to introduce predetermined recesses into a work piece, fundamentally the required geometric relationships between the work piece and the tools have to be established. For example, if a centered work piece is fastened in a vice that lies freely displaceably on the table of an upright drill, the vice must be adjusted by the worker with one hand so that the bore tip lies exactly above the center point. The worker then operates the lever with the other hand to lower the drill spindle, in order to bore the intended hole. When the hole must have a predetermined depth, the worker will observe the scale provided on the drill spindle from which he can determine the extent of the lowering of the drill.
In order to provide the same work piece with the same bore, one can consider the use of a robot drill, which is equipped with an image recognition device that recognizes the position of the work piece automatically so that, with the aid of a computer program, one can determine how the robot head with the bore is to be directed and guided.
However, there are cases of application in which measurement technological access to the “work piece” to be worked on is difficult. Thus, for example it may be necessary to take a sample from an archeological find, for example from a mummy. Without extensive explanation of the necessity, let us presume that hereby the mummy may be opened only minimally.
In order to solve this task, one can use the so-called navigation system known from medical technology. This is a system with a navigation camera, which is able to recognize reference points in the room. If such reference points are attached to the tool and the work piece (in the medical area, on a part of the body) then, with the aid of the computer assigned to the camera, the spatial relationship between the work piece and the tool can be established. It is clear to the expert in the field that for this purpose the geometry of the tool and the work piece and the position of the reference point with respect to the tool and the work piece must be known. These working steps are sufficiently known because they can be taken from the operating procedures of the navigation systems. In order to produce a bore, it is thus possible to represent the work piece together with the tool on the provided virtual bore axis on a screen. The drill is now guided by hand so that its spatial position and its forward movement (drill feed movement) coincide with the virtual bore axis. Hereby the operator must look at the monitor that is away from the actual relevant working area, to align and move the tool until the actual position and the target position are identical. This hand-eye coordination is stressful and presumes good spatial imagination and much training.
This technique is described in documents U.S. Pat. No. 6,226,548; U.S. Pat. No. 6,747,646; U.S. Pat. No. 6,725,080; U.S. Pat. No. 6,697,664; U.S. Pat. No. 6,535,756; U.S. Pat. No. 6,470,207; U.S. Pat. No. 6,205,411. In addition to the most frequently used optical navigation cameras, the position and orientation recognition can also be performed using ultrasound-based or electromagnetic detection methods, among others, as described, for example, in the document U.S. Pat. No. 6,503,249. However, the basic principles outlined above are identical.
In order to relieve the person performing the job (worker or operator), called operator below, from the difficult hand-eye coordination, there is the possibility of using mechanical calibers that guide the tool mechanically, for example the drill or the saw blade, so that he operator has to perform only one movement, for example with one single degree of freedom. The difficulty in this technique consists in the aligning and fixing of the mechanical caliber in the correct geometrical position with respect to the work piece or with respect to the body part to be worked on. In principle, this is possible with a robot described in document U.S. Pat. No. 6,837,892 in combination with a navigation system.
However, there are cases of application in which a robot is not suitable due to its size (unwieldiness), its weight and its mechanical sensitivity. Such cases occur in the medical as well as in the non-medical area. For example, it is clear to the person skilled in the art that such a robot is not very suitable, for example, when a mummy is to be investigated which is located in the crypt of a pyramid or when a medical operation must be performed on a living human and a cumbersome robot is to be kept sterile.
Therefore, the task of the invention is to provide a technique for guiding a tool that makes guiding of the tool possible, for example, in the sense of a drill caliber or an installation for applying a saw. Hereby the tool should be directed by a tool guiding element in such a way that the tool penetrates into the work piece in the intended spatial orientation.